Katsushi Kanamori

In vivo viscoelastic behavior in the human aorta.

To characterize the viscoelastic properties of the human aorta in vivo, the pressure-diameter relation was determined in the abdominal aorta in 15 subjects. Diameter was measured noninvasively with a highly sensitive ultrasonic displacement meter, while intra-aortic pressure was measured with a catheter tip micromanometer inserted from the femoral artery. The frequency-dependent changes in the pressure-strain modulus (Ep) of the aorta and the phase lag of diameter to pressure were calculated by frequency analysis of these wave forms at the mean blood pressure of 109 mm Hg. The Ep and the phase lag at the fundamental frequency component (1.2 +/- 0.3 Hz, mean +/- SD) were (1.52 +/- 0.57) x 10(6) dyne/cm2 and -6.7 degrees +/- 2.1 degrees, respectively. Although the phase lag at the fundamental frequency was in good agreement with the published in vitro data, the calculated phase lags above the second harmonic were inconsistent, which was probably due to the nonlinearity in the pressure-diameter relation. To separate the effect of this nonlinearity, analysis was conducted with a model consisting of a static nonlinear component representing the elasticity and a dynamic linear component representing the viscosity. This method of analysis revealed that the phase lag due to the viscous component provided relatively flat frequency response to the 10th harmonic. It was confirmed that the aortic wall viscosity showed no apparent difference between the in vivo and the in vitro experimental conditions.

Relationship between lipids and angiographically defined coronary artery disease in Japanese patients

The relationship between the severity and extent of coronary artery disease (CAD) and the lipid profiles was evaluated in 120 Japanese male patients, who underwent coronary angiography. Analysis of the lipid quartile distribution showed that the percentage of patients with significant CAD increased as the total cholesterol (TC) increased and high-density lipoprotein cholesterol (HDL-C) decreased. In addition, as the number of vessels with marked coronary artery stenosis increased, TC and TC/HDL-C increased while HDL-C decreased. However, within this population, triglyceride level, high blood pressure, and smoking were not significantly associated with coronary angiographic findings.